1. Field of the Invention
This invention relates to a magnetoresistance thin film magnetic head which is suitable for reproducing signals recorded in a hard disc and to a bias characteristics measuring method therefor.
2. Description of the Related Art
For a reproducing head of a hard disc drive or a driving device, a magnetoresistance thin film magnetic head exhibiting high sensitivity to short wavelength signals, hereinafter referred to as an MR head, is employed in general.
The MR head is a reproducing head utilizing a phenomenon of magnetoresistance effect in which electrical resistance varies in accordance with an angle formed by the direction of magnetization with the direction of an internal current. In the MR head, an MR magnetic thin film receives a leakage magnetic flux from a magnetic recording medium, having its direction of magnetization turned by the magnetic flux. The direction of magnetization forms an angle corresponding to the magnetic property with the direction of the current running through the inside of the MR magnetic thin film. Therefore, the electrical resistance of the MR magnetic thin film changes, and a change in voltage corresponding to the change in the electrical resistance appears at electrodes at both ends of the MR magnetic thin film. Thus, the magnetically recorded signals can be read out as voltage signals.
The MR head, if used as the reproducing head of the hard disc drive, has a shielding construction in which a magnetoresistance effect magnetic sensing section 54 and a bias conductor 55 are sandwiched between a pair of magnetically shielding thin film magnetic cores 56, 57 via an insulating layer 58, as shown in FIGS. 1 and 2. The magnetoresistance effect magnetic sensing section 54, hereinafter referred to as an MR magnetic sensing section, consists of a magnetoresistance effect thin film formed by stacking electrodes 52, 53 on a distal end and a rear end, respectively, of an air bearing surface (ABS) 51, that is, a surface facing the hard disc, while the bias conductor 55 provides a magnetized status in a predetermined direction for the MR magnetic sensing section 54. The MR head of the above construction is loaded to be used on a slider member 59 of Al.sub.2 O.sub.3 --TiC or the like.
In the MR head of such construction, for reproduction of signals, direct currents are supplied as sense currents from the distal end electrode 52 and the rear end electrode 53 of the MR magnetic sensing section 54, while a direct current is supplied to the bias conductor 55 for generating a biased magnetic field. Accordingly, terminals 60, 61, 62, 63 for connection to a direct current power source are provided on the edges of the distal end electrode 52 and the rear end electrode 53 and both edges of the bias conductor 55, respectively. Thus, a total of four terminals are disposed on the slider member 59.
However, in the MR head of the above construction, the necessity of disposing the four terminals 60, 61, 62, 63 on the slider member 59 causes large obstruction to diminution of the hard disc drive in size and achievement of low levitation.
That is, the head employed in the hard disc drive further includes an inductive head for recording stacked on the MR head for reproduction. In the inductive head, a thin film magnetic core on the upper layer shielding the MR magnetic sensing section as one thin film magnetic core constituting a closed magnetic circuit and the other thin film magnetic core stacked to face the one thin film magnetic core have their respective magnetically connecting sections spirally surrounded by a head coil. From both ends of the head coil of the inductive head, two terminals are led, respectively, for supplying currents based on recorded information. Therefore, with the MR head of the above construction, a total of six terminals are disposed on the slider member 59, that is, the four terminals 60, 61, 62, 63 of the MR head plus the two terminals 65, 66 of the inductive head, as shown in FIG. 3.
For disposing as many terminals as six on the slider, however, it is necessary to reduce the terminals in size and to shorten the distance between the terminals. Therefore, there are difficulties in terminal formation and bonding processing on formation of a leader line. Such difficulties become even more serious particularly when the slider is to be reduced in size.
For achieving low levitation of the head, a constant levitation attitude of the slider is strictly required. However, the rigidity of the large number of terminals formed on the slider causes difficulties in the slider's being in a constant leviation attitude. This is disadvantageous to achievement of low leviation.
For this reason, an attempt has been made to reduce the number of terminals disposed on the slider to 5, using one terminal for one of the terminals led from the bias conductor as well as for one of the terminals led from the MR magnetic sensing section. However, even though the number of terminals disposed on the slider is reduced to 5, three terminals are disposed to form one line and the remaining two terminals are disposed to form another line, requiring a disposition area substantially equal to that for 6 terminals. Thus, it is far from a significant reduction in size of the slider.